CORRECTION...a spongy brake pedal does NOT mean a bad master cylinder...a LOW or SINKING pedal are signs the master cylinder is failing.
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And leaking POWER STEERING fluid will NEVER cause a master cylinder to fail!

when my hydro booster ran out of power steering fluid my break started to failhey vehicle with hydro booster has a ride to actuatesyour breakmaster cylinder I do not know which one is going outso I believe that the booster does affect your master cylinder